Progress has conventionally been made in electronically controlling various devices that are mounted in a vehicle. In step with this, electric actuators such as motors and solenoids are in wide use to convert an electrical signal into mechanical motion or hydraulic pressure. It is necessary to detect a fault in a load-driving circuit that drives current flowing through these electric actuators to control the electric actuators safely.
As a general method for detecting a fault in the load-driving circuit, there is a method for detecting a short circuit state of the load-driving circuit by inserting a current sense resistor in series between the load-driving circuit targeted for detection and a load and measuring the voltage across the current sense resistor. However, there is a problem with such a method that a loss of power occurs due to the current sense resistor. Hence, a method is known in which a current detection circuit including a small current sense transistor and the like is connected in parallel to a driver transistor that drives an electric actuator targeted for control to detect the current flowing through the current detection circuit and accordingly the detection of fault in the load-driving circuit is achieved with a small loss.